Process for making tetramethyl lead



Patented Jan. 8, i963 ice 3,072,695 PRQCESS FOR MAltiN TETRAMETHYL LEAD Victor Tuilio, Wilmington, DeL, assignor to E. I. du Pont de Nemours and Company, Wiimington, Del., a corporation of Deiawa're I No Drawing. Filed Nov. 25, 1960, Ser. No. 71,404 26 Ciaims. (Cl. 260-437) This invention relates to a process for the manufacture of tetramethyl lead, particularly by the reaction of a methyl halide with a sodium lead alloy in the presence of a catalyst.

It is well known that tetraalkyl lead compounds .are useful an antiknock agents in fuels forinternal "combustion engines. Up to the present time, tetraethyl lead'has been manufactured and used predominantly. However, tetramethyl lead, particularly because of its higher .volatility, can be used advantageously as an antiknock agent in motor fuels, alone orin combination with .tetraethyl lead and the like in varying proportions toimprove the road performance of leaded fuels, as more fully described by Smyers et al. in U.S. Patent 2,310,376. Calingaert et al. in US. Patent 2,270,109, disclose a process for preparing a mixture of tetramethyl and ethyl lead compounds by reacting a mixture of methyl chloride and ethyl chloride with sodium lead alloy in the presence of an aluminum type catalyst. Such process results in a mixture of five tetraalkyl lead compoundsin which tetramethyl lead is present in a minor proportion. The process of Calingaert et al. does not constitute an economical process for making pure or substantially pure tetramethyl lead in large quantities and does not yield the combination of tetraalkyl lead compounds in the proportions required for many purposes disclosed by Smyers et al.

The manufacture of tetramethyl lead by the general alkyl halide-sodium lead alloy reaction requires special conditions. Whereas the ethyl chloride-sodium lead alloy system does not require catalysis and can be accelerated by such substances as ketones, alcohols, acetals, etc. known in the art, the methyl chloride-lead alloy system responds not at all or poorly to the presence of such ac celerators and to conditions otherwise conducive to the formation of tetraethyl lead. Methyl halides are unique in that only certain catalysts of the aluminum type seem effective to bring about the formation of methylated lead compounds. Even so, the aluminum type catalysts present practical difliculties in commercial scale operation. For example, an induction period is generally encountered before the methylation begins, using the combination of aluminum alloy and aluminum chloride described by Calingaert et al. in US. Patent 2,270,109 for the manufacture of mixed methyl and ethyl leads from mixtures of methyl and ethyl chlorides. Also, relatively high temperatures (100 C.ll C.) are required to achieve satisfactory yields of tetrarnethyl lead. The induction period and the high reaction temperature together present the hazard of sudden and uncontrollable reaction (i.e. surges in temperature and pressure) once the exothermic methylation begins. This can be particularly serious with tetr methyl lead because of the relative ease with which it can decompose explosively. Aluminum plus aluminum chloride catalysts are ineffective in at least one of the following respects, to avoid the induction period, to initiate reaction at low temperatures, to provide satisfactory reaction control, and to produce tetramethyl lead in good yield safely and in short time.

Other aluminum type catalysts suggested by Calingaert et al., for example, trimethyl aluminum, dimethyl aluminum chloride and the like, have the disadvantages for commercial use of being difiicult and hazardous to handle because of their extreme sensitivity'to air and to moisture. On the other hand, it is desirable to be ableto use alumi;

num chloride which is commercially available and presents no unusual storage and handling problems, provided satisfactorily high yields and tetramethyl lead can be obtained with it.

It is an object of this invention to provide a new and improved process for the manufacture of tetramethyl lead. Another object is to provide such a process which is particularly adapted for the large scale manufacture of pure or substantially pure tetramethyl lead. Still another object is to provide such a process which employs a novel aluminum type catalyst. A further object is to provide a catalytic process for reacting a methyl halide with a sodium-lead alloy wherein the reaction is initiated without an induction period and proceeds smoothly at relatively low temperatures to produce tetramethyl lead in good yield. A still further object is to provide a process for making tetramethyl lead which utilizes an aluminum halide catalyst in combination with an additional agent which materially improves the yield of tetramethyl lead. Other objects are to advance the art. Still other objects will appear hereinafter.

The above and other objects may be accomplished in accord with this invention which involves the process for making tetramethyl lead which comprises mixing at a temperature below 50 C. a sodium lead alloy, at least about 0.25 mole per mole of sodium of an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53, and, in an amount to provide from 0.003 to about 0.3 atom of aluminum per atom of sodium in said alloy, an aluminum-containing hydride of the group consisting of aluminum hydride, complex aluminum hydrides having the formula M(AlH wherein M is a metal of the group consisting of alkali metals and alkaline earth metals .and n is an integer corresponding to the valence of M, aluminum borohydride, alkyl aluminum hydrides having the formula R AlH wherein R is an alkyl radical of l to 10 carbon atoms and x is an integer of 1 to 2, and complex alkyl aluminum hydrides having the formula. M(R AlII wherein M is a metal of the group consisting of alkali metals and alkaline earth metals, n is an integer corresponding to the valence of M, R is an alkyl radical of 1 to 10 carbon atoms and y is an integer of 1 to 3, heating the mixture to a temperature of from 50 C. to about C. to initiate the methylation reaction, and then heating the mixture to a temperature of from about 70 C. to about C. and maintaining it at such temperature until the methylation reaction is substantially complete while gradually adding such quantities of said methyl halide as may be required to provide a total of at least one mole thereof for each mole of sodium. A particularly preferred method of this invention comprises employing, in combination with the aluminum-containing hydride in the above process, an aluminum halide in which the halogen has an atomic number in the range of 17 to 53 in a proportion of about 1 mole for each 1 to 5 moles of the aluminum-containing hydride.

It has been found that by carrying out the reaction in such manner, material advantages and improved results are obtained. The aluminum-containing hydrides constitute a new class of aluminum type catalysts for eifecting the methylation reaction. The complex aluminum hydrides of the formula M (AIH have the advantage (over the other hydrides and other trialkyl aluminums and alkyl aluminum sesquihalides) of being fairly stable under ordinary atmospheric conditions and thus are rather easily stored and handled. When used as the sole catalysts for the methylation reaction, the aluminum-containing hydrides exhibit an induction period. However,

by mixing them with the sodium lead alloy and the methyl halide at temperatures below 50 C. and then heating 'reaction.

J the mixture to a temperature of 50 C. to about 70 C. until the reaction is well started, the methylation can be readily controlled and the hazards presented by the prior processes can be largely reduced.

When an aluminum halide is employed in combination with the aluminum-containing hydride and both are present when the reaction mixture is subjected to reaction conditions, particularly to temperatures of from 50 C. to about 70 C., the reaction is initiated promptly without an induction period. In other words, the presence of the combination of catalysts provides a smooth and safe initiation of the methylation reaction promptly' at relatively low temperatures and ensures a smooth and controlled This is particularly important at the beginning when the mixture is heated to start the reaction. The absence of the induction period when the two types of catalyst are used in combination is partcularly surprising in view of the substantial induction period encountered when either is used without the other. In addition, the use of the combination of catalysts to initiate the reaction also provides the unexpected benefit of increased yields of tetramethyl lead.

Broadly, the overall process comprises mixing the sodiagitation to a temperature at which the reaction is initiated and, when the reaction has become well started, gradually raising the temperature to one at which the reaction proceeds at a reasonable rate, completing the reaction at the higher temperature, and then recovering the tetramethyl lead from the reaction mixture by con-' ventional procedures. Also, as is conventional in the preparation of tetraalkyl lead compounds by the reaction of alkyl halides with sodium lead alloys, the reac-'' tion is carried out under substantially anhydrous conditions and in the absence of air and oxygen, i.e. with anhydrous reactants while excluding air, oxygen, moisture and the like from the reactor, in the manner well known to the art.

, Reaction temperatures are usually in the range of from 50 C. to about 130 C. and, for reasons of safety, the pressure preferably should be kept below about 500 p.s.i.g., for example, by cooling, controlling the rate of heating and/ or the amount of methyl halide in the reaction zone, and by venting. The reaction requires one mole of methyl halide for each mole of sodium in the sodium lead alloy. The reaction may be initiated with all of the desired amount of methyl halide present or with a fraction of the required amount of methyl halide present, followed by gradual addition of the rest of the desired amount as the reaction proceeds.

The alkylating agent employed will consist of a methyl halide in which the halogen has an atomic number in the range of 17 to 53, i.e. methyl chloride, methyl bromide, or methyl iodide, or a mixture of 2 or more methyl halides. Preferably, the reaction will be carried out with methyl chloride and monosodium lead alloy, NaPb. The total amount of methyl halide employed will be at least one mole and usually not more than 20 moles thereof per mole of sodium as sodium lead alloy, and preferably from about 1.1 to about 5 moles of methyl halide per mole of sodium. When it is desired to gradually add the methyl halide during the reaction, it is best to have present at the initiation of the reaction frcm about 0.25 to about 0.50 mole of methyl halide per mole of sodium, preferably about 0.50 mole, and to gradually add the rest of the methyl halide after the reaction has been initiated. Larger amounts than about 1.5 moles of the methyl halide can be used to dilute the reaction mass and aid in controlling the reaction temperature. Similarly, the methyl halide can be carried in an inert solvent, such as the hydrocarbons, hexane, benzene, toluene and the like, to dilute the reaction mass.

The process requires, as a catalyst, an aluminum-containing hydride of the group consisting of aluminum hydride, complex aluminum hydrides having the formula M(AlH wherein M is a metal of the group consisting of alkali metals and alkaline earth metals and n is an integer corresponding to the valence of M, aluminum borohydride, alkyl aluminum hydrides having the formula R,,AlI-I wherein R is an alkyl radical of 1 to 10 carbon atoms and x is an integer of 1 to 2, and complex alkyl aluminum hydrides having the formula wherein M is a metal of the group consisting of alkali metals and alkaline earth metals, n is an integer corresponding to the valence of M, R is an alkyl radical of 1 to 10 carbon atoms and y is an integer of 1 to 3. It will be understood that, as used herein, the term alkali metal means lithium, sodium, potassium, rubidium and caesium, and the term alkaline earth metal" means calcium, strontium, barium and magnesium.

Aluminum-containing hydrides suitable for use as catalysts in the process of this invention can be obtained by reacting an aluminum halide with either (a) an alkali metal hydride or an alkaline earth metal hydride or (b) an alkali metal aluminum hydride or an alkaline earth metal aluminum hydride, as more particularly described by Schlesinger et al., in US. Patent 2,567,972. They may also be prepared by the method described by Redman in US. Patent 2,885,314, involving direct reaction of hydrogen at elevated temperature and pressure with aluminum activated by an alkyl aluminum.

Complex aluminum hydrides that may be regarded as molecular complexes or compounds of aluminum hydride, AlH with other metallic hydrides, may also be used as catalysts for the methylation reaction. Included are the alkali metal aluminum hydrides and the alkaline earth metal aluminum hydrides, M(AlH where M stands for the alkali metal or the alkaline earth metal and n is 1 or 2, corresponding to the valence of M. Such complex hydrides and their preparation are described by Schlesinger et al. in US. Patent 2,567,972. Representative examples are lithium aluminum hydride, sodium aluminum hydride, and magnesium aluminum hydride.

Another complex aluminum hydride that may be used is aluminum borohydride, which may be prepared by the reaction of'an aluminum halide with an alkali metal borohydride, conveniently as described by Hinkamp in US. Patent 2,854,312.

Similarly there may be used, as catalysts for the methylation reaction, aluminum hydrides wherein one or two hydrogen atoms are replaced by alkyl groups to provide alkyl aluminum hydrides having the formula R,,AlH where R is an alkyl radical of 1 to 10 carbon atoms and x is an integer of 1 to 2, and complex alkyl aluminum hydrides having the formula M(R AlH where M is an alkali metal or an alkaline earth metal, n is an integer corresponding to the valence of M, y is an integer of 1 to 3, and R is an alkyl radical of 1 to 10 carbon atoms, said alkyl radicals being represented by methyl, ethyl, butyl, hexyl, and decyl. These hydrides and the methods for preparing them are disclosed in US. Patent 2,915,541, British Patent 774,516, US. Patent 2,765,329, and by Ziegler et al. in Ber. 42, 2320-2332 (1959) and in Ann. (Liebigs) 629, 33-49 (1960).

The use of the complex aluminum hydrides, M(AlH where M is an alkali metal or an alkaline earth metal, such as lithium aluminum hydride or magnesium aluminum hydride, constitutes a preferred embodiment. In contrast to trialkyl aluminums, alkyl aluminum sesquihalides, the alkyl aluminum hydrides and the complex alkyl aluminum hydrides, which tend to ignite spontaneously in air, particularly moist air, these complex tetrahydrides are reasonably stable under ordinary atmospheric conditions and thus are rather easily stored, handled, and transported into the methylation reaction zone. A preferred embodiment of the invention is the use of a complex aluminum hydride, e.g. LiAlH in combination with an aluminum halide catalyst, such as AlCl such combination providing for smooth and rapid initiation of the reaction without an induction period and resulting in high yields of tetramethyl lead. Such combination is particularly advantageous in that each component is available commercially and is easily handled under ordinary atmospheric conditions.

As catalyst for the methylation reaction, the aluminumcontaining hydride or mixtures of two or more thereof normally will be used in amounts providing from about 0.003 to about 0.3 atom of Al per atom of Na in the sodium lead alloy, preferably from about 0.01 to about 0.1 atom of Al per atom of Na. With LiAlH as the hydride source of aluminum, the broad range amounts to about 0.05% to about 5% of the hydride by weight of the alloy as NaPb, and the preferred range amounts to about 0.17% to about 1.25%.

The aluminum halides, which can be used in combination with the aluminum-containing hydrides in the process of this invention, are those in which the halogen has an atomic number in the range of 17 to 53. The term aluminum halide is used in its strict sense to mean the compounds which consist of aluminum and halogen, i.e. AlCl AlBr and A11 Aluminum chloride is preferred. Mixtures of two or more of the aluminum halides may be used. Ordinarily, the aluminum halide will be employed in a proportion of about 1 mole for each 1 to 5 moles of the aluminum-containing hydride, preferably for each 2 to 4 moles, particularly for about 3 moles of a complex hydride such as LiAlH With AlCl as the halide and LiAlH as the hydride, about equal weights of each provide the particularly preferred combination. These ingredients can be added to the reactor for the methylation reaction separately in any order or they can be mixed beforehand, it being understood in this regard that the hydride and the halide can be caused to react to produce aluminum hydride in accordance with the following equation The aluminum-containing hydride catalyst, with or without aluminum halide, can be used as such or added as a suspension, slurry, or solution in small amounts to an inert liquid carrier, such as hexane, benzene, toluene, and kerosene. Similarly, the aluminum halide, when added separately, can be added along with the above solvents or in liquefied methyl chloride. Normally, however, as lithium aluminum hydride and aluminum chloride are reasonably stable and easily handled solids, these preferred substances are added as such. While these substances are fairly stable under ordinary atmospheric conditions, it is preferred to minimize their contact with air and moisture, in short, to maintain them under inert atmospheres, e.g. nitrogen or methane, and to exclude moisture. Occasionally, it is found that the commercial grade I of anhydrous aluminum chloride is less active than desired, perhaps due to its having been unduly exposed to moist air. Such material can be reactivated by treatment with dry hydrogen chloride.

It is essential for the purposes of this invention and to obtain the advantageous results thereof that the aluminumcontaining catalyst or catalysts be present in the reactor with the sodium lead alloy and at least part of the methyl halide when the mixture is subjected to reaction conditions. Accordingly, at least part of the methyl halide and the other components are mixed at a temperature below 50 C., usually at room temperature or below, i.e. about 20 C. to about C. and below, and then the mixture is heated to the temperature required for initiation of the reaction. The methylation reaction can be initiated smoothly at temperatures of C. to about 70 C. The reaction can be completed at such temperatures. However, the reaction tends to be undesirably slow at such temperatures, and it is usually desirable to employ Cir higher temperatures of from about C. to about 130 C. for completion of the reaction, and preferably temperatures of from about C. to about C. for rapid completion of the reaction safely.

The importance of these results is that a greater degree of safety is achieved and at a lower operating cost, considering the hazards and expense of using pressurized equipment and having a relatively unstable product such as tetramethyl lead confined at elevated temperatures. To be able to control temperatures and pressures is particularly important in the early stages of the reaction where the danger of a runaway reaction is greatest. Once at least 0.5 mole of methyl halide has reacted with the sodium lead alloy, the danger is greatly lessened and the temperatures can be more rapidly increased to the higher temperatures where the reaction takes place at the optimum rate. In general, the rate of heating and the pressure rise resulting therefrom are coordinated to prevent sharp increases therein, the temperature being raised gradually to the desired maximum temperature. This gradual rise in temperature, if not too rapid, may be continuous from the temperature of mixing the ingredients through the reaction initiation stage to the temperature desired for rapid completion of the reaction, or may be intermittent, as desired.

The reaction is effected under agitation. It is usually desirable to carry out the reaction in the presence of an inert solid, such as graphite or silica, as an internal lubricant, mixing aid, or anti-agglomerant for lead, since ordinarily the reaction mass tends to be somewhat diflicult to stir, probably due to the inherent tendency of the particles of free lead to stick together. From about 1% to about 20% by weight of the alloy are used, depending on the dimensions of the reactor, the effectiveness of the agitation means, and the proportions of the reactants.

In practice, the methyl halide is simply added to a reactor which will also contain the sodium lead alloy, the aluminum-containing hydride, the aluminum halide (when used), and usually an internal lubricant, such as graphite, at about room temperature. In a typical run, an auto clave is loaded at room temperature to contain 35 pounds (about 1.5 moles per mole of sodium) of methyl chloride, 0.6 pound LiAlH 0.6 pound of AlCl and 3 pounds of graphite per 100 pounds of comrninuted NaPb alloy, added in any order. Reaction is effected under agitation and pressure by heating to a temperature at which the methylation begins and can be maintained safely at a practical rate. The rate of heating and the pressure rise (as a result of heating) are coordinated to prevent sharp increases. Reaction mass temperature is controlled, by cooling the autoclave when necessary, to keep the internal pressure from exceeding about 500 p.s.i.g. Usually, a temperature of about 50 C.70 C. has to be reached to initiate the methylation, and, once the exothermic reaction has started and is able to be controlled by the cooling means, the temperature is allowed to rise (or is raised) to 100 C.130 C. and held there until the reaction is complete.

Alternatively, the methyl chloride can be fed gradually into the autoclave containing the other components. Preferably, about 0.25 to about 0.50 mole of methyl chloride per mole of sodium is added before the charge is brought to 50 C.-70 C. where reaction begins. The rest of the methyl chloride is then fed in slowly and the temperature allowed to increase to 100 C.130 C. where the reaction is completed, the pressure being kept under about 500 p.s.i.g. by cooling, controlling the methyl chloride feed, and venting of non-condensibles.

To recover the product, the charge is cooled to about 20 C.30 C. and residual methyl halide vented to a recovery system, as in tetraethyl lead technology. The tetramethyl lead component can be recovered by solvent extraction, e.g. with toluene, or by steam distillation, according to the well-known methods.

In order to more fully illustrate this invention, preferred modes of carrying it into effect, and the advantageous results to be obtained thereby, the following examples are given in which the amounts and proportions are by weight, except where otherwise specifically indicated.

Example 1 A steel bomb is charged under nitrogen to contain 2.5 parts of graphite, 1.25 parts of lithium aluminum hydride, and 100 parts of comminuted monosodium lead alloy. (The atom ratio of Al as hydride to Na as alloy is 0.075: 1.). Then, 77.5 parts of methyl chloride are added to the bomb cooled with solid carbon dioxide and the bomb closed. In this system, the total volume of the bomb is such that the amount of methyl chloride corresponds to 0.31 gram per cubic centimeter.

The bomb, which is equipped with thermocouples to record the internal temperature (i.e. the temperature of the reaction mass), is warmed to room temperature, then jacketed with heating oil, which is heated at a steady rate from room temperature to 110 C. in 26 minutes and then held at 110 C. for 1 hour. Simultaneously with the start of heating, the bomb is vigorously agitated and the internal temperature of the reaction mass is recorded. The internal temperature, paralleling that of the heating oil, is 110 C. after. 26 minutes and remains at 110 C. for another 10 minutes before beginning to rise. Over a 5 minute period, the reaction mass rises to a maximum of 132 C., then cools gradually during 30 minutes to the temperature of the heating oil (maintained at 110 C.), where it is held for minutes. The bomb is cooled and opened. Tetramethyl lead is obtained in 71% yield.

Example 2 The procedure of Example 1 is repated except that only one-half of the above amount of lithium aluminum hydride (0.038 atom of Al per atom of Na) is added to the reactor, and there is also added an equal weight (0.625 part) of aluminum chloride. The time for raising the temperature of the heating oil surrounding the reactor to 110 C. is 26 minutes. However, the reaction mass develops an internal temperature of 110 C. in only 16 minutes (indicating the exothermic reaction is well started), and 5 minutes later reaches a maximum temperature of 126 C., which decreases gradually to 110 C. during another 30 minutes. Finally, the bomb is held at 110 C. for minutes, cooled and opened. Tetramethyl lead is obtained in 75% yield.

Comparing the above examples, the method of Example 2, using the complex aluminum hydride methylation catalyst of Example 1 in combination with an aluminum halide methylation catalyst, appears to involve no induction period and to afford tetramethyl lead in significantly better yield.

The combination of the complex hydride and the aluminum halide is particularly effective in low concentrations. For example, in a repeat of Example 2 with the addition of only 0.25 part of lithium aluminum hydride (0.015 atom Al per atom of Na) and 0.25 part of aluminum chloride, the reaction proceeds smoothly to give tetramethyl lead in 84% yield. In contrast, with aluminum chloride as the sole catalyst in an amount of 1.25 parts per 100 parts of the alloy in the above procedure, the yield of tetramethyl lead is 80%, and when 0.63 part of the aluminum chloride is used the yield is only 52%.

Tetramethyl lead may be obtained on employing as the hydride in the above examples aluminum hydride, sodium aluminum hydride, magnesium aluminum hydride, or aluminum borohydride or mixtures thereof, in amounts corresponding to from about 0.003 to 0.3 atom of Al as hydride for each atom of Na in the sodium lead alloy. Also, similar results may be obtained by replacing aluminum chloride in Example 2 by the molar equivalent amount of aluminum bromide or aluminum iodide. Also, all or part of the methyl chloride in Examples 1 and 2 may be replaced by the molar equivalent amount of methyl bromide or methyl iodide or mixtures thereof, to obtain good yields of tetramethyl lead.

It will be understood that the preceding examples have een given for illustrative purposes solely and that this invention is not restricted to the specific embodiments described therein. On the other hand, it will be readily apparent to those skilled in the art that, subject to the limitations set forth in the general description, many variations can be made in the materials, proportions, conditions and techniques employed, without departing from the spirit and scope of this invention.

From the preceding description and examples, it will be apparent that this invention provides a new and improved process for making tetramethyl lead in high yields which process overcomes the difficultics and hazards involved in the prior processes. Particularly, this invention eliminates the induction period ordinarily encountered in prior processes and/or the hazards involved therein, and permits the initiation of the reaction at lower temperatures in a smooth and safe manner and the reaction to be readily controlled. It produces tetramethyl lead as the predominant product and makes it possible to safely and economically produce pure or substantially pure tetramethyl lead in high yields. Accordingly, it will be apparent that this invention constitutes a valuable advance in and contribution tothe art.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows.

I claim:

1. The process for making tetramethyl lead which comprises mixing at a temperature below C. a sodium lead alloy, at least about 0.25 mole per mole of sodium of an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53, and, in an amount to provide from 0.003 to about 0.3 atom of aluminum per atom of sodium in said alloy, an aluminum-containing hydride of the group consisting of aluminum hydride, complex aluminum hydrides having the formula M(AlH wherein M is a metal of the group consisting of alkali metals and alkaline earth metals and n is an integer corresponding to the valence of M, aluminum borohydride, alkyl aluminum hydrides having the formula R AlH wherein R is an alkyl radical of 1 to 10 carbon atoms and x is an integer of 1 to 2, and complex alkyl aluminum hydrides having the formula M(R AlH wherein M is a metal of the group consisting of alkali metals and alkaline earth metals, 1: is an integer corresponding to the valence of M, R is an alkyl radical of 1 to 10 carbon atoms and y is an integer of 1 to 3, heating the mixture to a temperature of from 50 C. to about C. to initiate the methylation reaction, and then heating the mixture to a temperature of from about 70 C. to about C. and maintaining it at such temperature until the methylating reaction is substantially complete while gradually adding such quantities of said methyl halide as may be required to provide a total of at least one mole thereof for each mole of sodium.

2. The process for making tetramethyl lead which comprises mixing at a temperature below 50 C. a sodium lead alloy, at least about 0.25 mole per mole of sodium of an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53, and, in an amount to provide from 0.003 to about 0.3 atom of aluminum per atom of sodium in said alloy, a complex aluminum hydride having the formula MAlH wherein M is an alkali metal, heating the mixture to a temperature of from 50 C. to about 70 C. to initiate the methylation reaction, and then heating the mixture to a temperature of from about 70 C. to about 130 C. and maintaining it at such temperature until the methylat- 5 ing reaction is substantially complete while gradually adding such quantities of said methyl halide as may be required to provide a total of at least one mole thereof for each mole of sodium.

3. The process for making tetramethyl lead which comprises mixing at a temperature below 50 C. a sodium lead alloy, from about 0.25 to about 20 moles per mole of sodium of an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53, and, in an amount to provide from about 0.01 to about 0.1 atom of aluminum per atom of sodium in said alloy, a complex aluminum hydride having the formula MAlH wherein M is an alkali metal, heating the mixture to a temperature of from 50 C. to about 70 C. to initiate the methylation reaction, and then heating the mixture to a temperature of from about 70 C. to about 130 C. and maintaining it at such temperature until the methylating raction is substantially complete while gradually adding such quantities of said methyl halide as may be required to provide a total of from 1 to about 20 moles thereof for each mole of sodium.

4. The process for making tetramethyl lead which comprises mixing at a temperature below 50 C. a sodium lead alloy, from about 0.25 to about 20 moles per mole of sodium of an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53, and, in an amount to provide from about 0.01 to about 0.1 atom of aluminum per atom of sodium in said alloy, a complex aluminum hydride having the formula MAlH wherein M is an alkali metal, heating the mixture to a temperature of from 50 C. to about 70 C. to initiate the methylation reaction. and then heating the mixture to a temperature of from about 100 C. to about 130 C. and maintaining it at such temperature until the methylating reaction is substantially complete while gradually adding such quantities of said methyl halide as may be required to provide a total of from 1 to about 20 moles thereof for each mole of sodium.

5. The process for making tetramethyl. lead which comprises mixing at a temperature below 50 C. monosodium lead alloy, from about 0.25 to about 5 moles per mole of sodium of an alkylating agent which consists of methyl chloride, and, in an amount to provide from about 0.01 to about 0.]. atom of aluminum per atom of sodium in said alloy, lithium aluminum hydride, heating the mixture to a temperature of from 50 C. to about 70 C. to initiate the methylation reaction, and then heating the mixture to a temperature of from about 100 C. to about 130 C. and maintaining it at such temperature until the methylating reaction is substantially complete while gradually adding such quantities of said methyl chloride as may be required to provide a total of from 1 to about 5 moles thereof for each mole of sodium.

6. The process for making tetramethyl lead which comprises mixing at a temperature below 50 C. a sodium lead alloy, at least about 0.25 mole per mole of sodium of an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53, and, in an amount to provide from 0.003 to about 0.3 atom of aluminum per atom of sodium in said alloy, an aluminum-containing hydride of the group consisting of aluminum hydride, complex aluminum hydrides having the formula lvifitll l wherein M is a metal of the group consisting of alkali metals and alkaline earth metals and n is an integer corresponding to the valence of M, aluminum borohydride, alkyl aluminum hydrides having the formula R AlH wherein R is an alkyl radical of l to carbon atoms and x is an integer of 1 to 2, and complex alkyl aluminum hydrides having the formula M(l A.ll-I wherein M is a metal of the group consisting of alkali metals and alkaline earth metals, n is an integer corresponding to the valence of M, R is an alkyl radical of 1 to 10 carbon atoms and y is an integer of 1 to 3, and, for each 1 to 5 moles of said aluminum-containing hydride, about 1 mole of an aluminum halide in which the halogen has an atomic number in the range of 17 to 53, heating the mixture to a temperature of from 50 C. to about 70 C. to initiate the methylation reaction, and then heating the mixture to a temperature of from about 70 C. to about 130 C. and maintaining it at such temperature until the methyiating reaction is substantially complete while gradually adding such quantities of said methyl halide as may be required to provide a total of at least one mole thereof for each mole of sodium.

7. The process for making tetramethyl lead which comprises mixing at a temperature below 50 C. a sodium lead alloy, at least about 0.25 mole per mole of sodium of an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53, and, in an amount to provide from 0.003 to about 0.3 atom of aluminum per atom of sodium in said alloy, a complex aluminum hydride having the formula MAlI-L; wherein M is an alkali metal, and, for each 1 to 5 moles of said complex aluminum hydride, about 1 mole of an aluminum halide in which the halogen has an atomic number in the range of 17 to 53, heating the mixture to a temperature of from 50 C. to about 70 C. to initiate the methylation reaction, and then heating the mixture to a temperature of from about 70 C. to about 130 C. and maintaining it at such temperature until the methylating reaction is substantially complete while gradually adding such quantities of said methyl halide as may be required to provide a total of at least one mole thereof for each mole of sodium.

8. The process for making tetramet-hyl lead which comprises mixing at a temperature below 50 C. a sodium lead alloy, from about 0.25 to about 20 moles per mole of sodium of an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53, and, in an amount to provide from about 0.01 to about 0.1 atom of aluminum per atom of sodium in said alloy, a complex aluminum hydride having the formula MAE-I wherein M is an alkali metal, and, for each 2 to 4 moles of said complex aluminum hydride, about 1 mole of an aluminum halide in which the halogen has an atomic number in the range of 17 to 53, heating the mixture to a temperature of from 50 C. to about 70 C. to initiate the methylation reaction, and then heating the mixture to a temperature of from about 70 C. to about 130 C. and maintaining it at such temperature until the methylating reaction is substantially complete while gradually adding such quantities of said methyl halide as may be required to provide a total of from 1 to about 20 moles thereof for each mole of sodium.

9. The process for making tetrarnethyl lead which comprises mixing at a temperature below 5 0 C. a sodium lead alloy, from about 0.25 to about 20 moles per mole of sodium of an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53, and, in an amount to provide from about 0.0 1 to about 0.1 atom of aluminum per atom of sodium in said alloy, a complex aluminum hydride having the formula MAE-I wherein M is an alkali metal, and, for each 2 to 4 moles of said complex aluminum hydride, about 1 mole of an aluminum halide in which the halogen has an atomic number in the range of 17 to 53, heating the mixture to a temperature of from 50 C. to about 70 C. to initiate the mcthylation reaction, and then heatin the mixture to a temperature of from about C. to about C. and maintaining it at such temperature until the methylating reaction is substantially complete while gradually adding such quantities of said methyl halide as may be required to provide a total of from 1 to about 20 moles thereof for each mole of sodium.

10. The process for making tetramethyl lead which comprises mixing at a temperature below 50 C. monosodium lead alloy, from about 0.25 to about 5 moles per mole of sodium of an alkylating agent which consists of methyl chloride, and, in an amount to provide from about 0.01 to about 0.1 atom of aluminum per atom of sodium in said alloy, lithium aluminum hydride, and,

for each 2 to 4 moles of said lithium aluminum hydride, about 1 mole of aluminum chloride, heating the mixture to a temperature of from 50 C. to about 70 C. to initiate the methylation reaction, and then heating the mixture to a temperature of from about 100 C. to about 130 C. and maintaining it at such temperature until the methylating reaction is substantially complete while gradually adding such quantities of said methyl chloride as may be required to provide a total of from 1 to about 5 moles thereof for each mole of sodium.

11. The process for making tetramethyl lead which comprises mixing at a temperature below 50 C. a sodium lead alloy, at least about 1 mole per mole of sodium of an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53, and, in an amount to provide from 0.003 to about 0.3 atom of aluminum per atom of sodium in said alloy, an aluminum-containing hydride of the group consisting of aluminum hydride, complex aluminum hydrides having the formula M(Al1-I.,) wherein M is a metal of the group consisting of alkali metals and alkaline earth metals and n is an integer corresponding to the valence of M, aluminum borohydride, alkyl aluminum hydrides having the formula R AlH wherein R is an alkyl radical of 1 to carbon atoms and x is an integer of 1 to 2, and complex alkyl aluminum hydrides having the formula M(R AiH wherein M is a metal of the group consisting of alkali metals and alkaline earth metals, n is an integer corresponding to the valence of M, R is an alkyl radical of 1 to 10 carbon atoms and y is an integer of 1 to 3, heating the mixture to a temperature of from 50 C. to about 70 C. to initiate the methylation reaciton, and then heating the mixture to a temperature of from about 70 C. to about 130 C. and maintaining it at such temperature until the methylating reaction is substantially complete.

12. The process for making tetramethyl lead which comprises mixing at a temperature below 50 C. a sodium lead alloy, from about 1 to about 20 moles per mole of sodium of an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53, and in an amount to provide from 0.003 to about 0.3 atom of aluminum per atom of sodium in said alloy a complex aluminum hydride having the for mula MAlH wherein M is an alkali metal, heating the mixture to a temperature of from 50 C. to about 70 C. to initiate the methylation reaction, and then heating the mixture to a temperature of from about 70 C. to about 130 C. and maintaining it at such temperature until the methylating reaction is substantially complete.

13. The process for making tetramethyl lead which comprises mixing at a temperature below 50 C. a sodium lead alloy, from about 1 to about 5 moles per mole of sodium of an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the I range of 17 to 53, and, in an amount to provide from about 0.01 to about 0.1 atom of aluminum per atom of sodium in said alloy, a complex aluminum hydride having the formula MAlH wherein M is an alkali metal, heating the mixture to a temperature of from 50 C. to about 70 C. to initiate the methylation reaction, and then heating the mixture to a temperature of from about 100 C. to about 130 C. and maintaining it at such temperature until the methylating reaction is substantially complete.

14. The process for making tetramethyl lead which comprises mixing at a temperature below 50 C. monosodium lead alloy, from about 1 to about 5 moles per mole of sodium of an alkylating agent which consists of methyl chloride, and, in an amount to provide from about 0.01 to about 0.1 atom of aluminum per atom of sodium in said alloy, lithium aluminum hydride, heating the mixture to a temperature of from 50 C. to about 70 C. to initiate the methylation reaction, and then heating the mixture to a temperature of from about 100 C. to about 130 C. and maintaining it at such temperature until the methylating reaction is substantially complete.

15. The process for making tetramethyl lead which comprises mixing at a temperature below 50 C. a sodium lead alloy, at least about 1 mole per mole of sodium of an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53, and, in an amount to provide from 0.003 to about 0.3 atom of aluminum per atom of sodium in said alloy, an aluminum-containing hydride of the group consisting of aluminum hydride, complex aluminum hydrides having the formula M(AlH wherein M is a metal of the group consisting of alkali metals and alkaline earth metals and n is an integer corresponding to the valence of M, aluminum borohydride, alkyl aluminum hydrides having the formula R AlH wherein R is an alkyl radical of 1 to 10 carbon atoms and x is an integer of 1 to 2, and complex alkyl aluminum hydrides having the formula M(R AlH wherein M is a metal of the group consisting of alkali metals and alkaline earth metals, :1 is an integer corresponding to the valence of M, R is an alkyl radical of 1 to 10 carbon atoms and y is an integer of 1 to 3, and, for each 1 to 5 moles of said aluminumcontaining hydride, about 1 mole of an aluminum halide in which the halogen has an atomic number in the range of 17 to 53, heating the mixture to a temperature of from 50 C. to about 70 C. to initiate the methylation reaction, and then heating the mixture to a temperature of from about 70 C. to about 130 C. and maintaining it at such temperature until the methylating reaction is substantially complete.

16. The process for making tetramethyl lead which comprises mixing at a temperature below 50 C. a sodium lead alloy, from about 1 to about 20 moles per mole of sodium of an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53, and, in an amount to provide from 0.003 to about 0.3 atom of aluminum per atom of sodium in said alloy, a complex aluminum hydride having the formula MAlI-L, wherein M is an alkali metal, and, for each 1 to 5 moles of said complex aluminum hydride, about 1 mole of an aluminum halide in which the halogen has an atomic number in the range of 17 to 53, heating the mixture to a temperature of from 50 C. to about 70 C. to initiate the methylation reaction, and then heating the mixture to a temperature of from about 70 C. to about 130 C. and maintaining it at such temperature until the methylating reaction is substantially complete.

17. The process for making tetramethyl lead which comprises mixing at a temperature below 50 C. a sodium lead alloy, from about 1 to about 20 moles per mole of sodium of an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53, and, in an amount to provide from about 0.01 to about 0.1 atom of aluminum per atom of sodium in said alloy, a complex aluminum hydride having the formula MAlH wherein M is an alkali metal, and for each 2 to 4 moles of said complex aluminum hydride, about 1 mole of an aluminum halide in which the halogen has an atomic number in the range of 17 to 53, heating the mixture to a temperature of from 50 C. to about 70 C. to initiate the methylation reaction, and then heating the mixture to a temperature of from about C. to about C. and maintaining it at such temperature until the methylating reaction is substantially complete.

18. The process for making tetramethyl lead which comprises mixing at a temperature below 50 C. monosodium lead alloy, from about 1 to about 5 moles per 13 to a temperature of from 50 C. to about 70 C. to initiate the methylation reaction, and then heating the mixture to a temperature of from about 100 C. to about 130 C. and maintaining it at such temperature until the methylating reaction is substantially complete.

19. The process for making tetramethyl lead which comprises initiating at a temperature of from about 50 C. to about 70 C. the reaction of a sodium lead alloy and an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53 in the presence of from about 0.003 to about 0.3 atom of aluminum per atom of sodium in said alloy, said aluminum being in the form of an aluminum-containing hydride of the group consisting of aluminum hydride, complex aluminum hydrides having the formula M(A1H.,) wherein M is a metal of the group consisting of alkali metals and alkaline earth metals and n is an integer corresponding to the valence of M, aluminum borohydride, alkyl aluminum hydrides having the formula R AlH wherein R is an alkyl radical of 1 to carbon atoms and x is an integer of 1 to 2, and complex alkyl aluminum hydrides having the formula wherein M is a metal of the group consisting of alkali metals and alkaline earth metals, n is an integer corresponding to the valence of M, R is an alkyl radical of 1 to 10 carbon atoms and y is an integer of 1 to 3, then heating the mixture to a temperature of from about 70 C. to about 130 C. and maintaining the mixture at the latter temperature until the methylation reaction is substantially complete.

20. The process for making tetramethyl lead which comprises initiating at a temperature of from about 50 C. to about 70 C. the reaction of a sodium lead alloy and an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53 in the presence of from about 0.003 to about 0.3 atom of aluminum per atom of sodium in said alloy, said aluminum being in the form of a complex aluminum hydride having the formula MAlH wherein M is an alkali metal, then heating the mixture to a temperature of from about 70 C. to about 130 C. and maintaining the mixture at the latter temperature until the methylation reaction is substantially complete.

21. The process for making tetramethyl lead which comprises initiating at a temperature of from about 50 C. to about 70 C. the reaction of a sodium lead alloy and an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53 in the presence of from about 0.01 to about 0.1 atom of aluminum per atom of sodium in said alloy, said aluminum being in the form of a complex aluminum hydride having the formula MAlH wherein M is an alkali metal, then heating the mixture to a temperature of from about 100 C. to about 130 C. and maintaining the mixture at the latter temperature until the methylation reaction is substantially complete.

22. The process for making tetramethyl lead which comprises initiating at a temperature of from about 50 C. to about 70 C. the reaction of monosodium lead alloy and an alkylating agent which consists of methyl chloride in the presence of from about 0.01 to about 0.1 atom of aluminum per atom of sodium in said alloy, said aluminum being in the form of lithium aluminum hydride, then heating the mixture to a temperature of from about 100 C. to about 130 C. and maintaining the mixture at the latter temperature until the methylation reaction is substantially complete,

23. The process for making tetramethyl lead which comprises initiating at a temperature of from about 50 C. to about 70 C. the reaction of a sodium lead alloy and an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53 in the presence of from about 0.003 to about 0.3 atom of aluminum per atom of sodium in said alloy,

said aluminum being in the form of an aluminum-containing hydride of the group consisting of aluminum hydride, complex aluminum hydrides having the formula M(All-I wherein M is a metal of the group consisting of alkali metals and alkaline earth metals and n is an integer corresponding to the valence of M, aluminum borohydride, alkyl aluminum hydrides having the formula R AlH wherein R is an alkyl radical of 1 to 10 carbon atoms and x is an integer of 1 to 2, and complex alkyl aluminum hydrides having the formula M(R AlH., wherein M is a metal of the group consisting of alkali metals and alkaline earth metals, n is an integer correponding to the valence of M, R is an alkyl radical of 1 to 10 carbon atoms and y is an integer of 1 to 3, and, for each 1 to 5 moles of said aluminum-containing hydnide, about 1 mole of an aluminum halide in which the halogen has an atomic number in the range of 17 to 53, then heating the mixture to a temperature of from about 70 C. to about 130 C. and maintaining the mixture at the latter temperature until the methylation reaction is substantially complete.

24. The process for making tetramethyl lead which comprises initiating at a temperature of from about 50 C. to about 70 C. the reaction of a sodium lead alloy and an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53 in the presence of from about 0.003 to about 0.3 atom of aluminum per atom of sodium in said alloy, sa-id aluminum being in the form of a complex aluminum hydride having the formula MAlH wherein M is an alkali metal, and, for each 1 to 5 moles of said complex aluminum hydride, about 1 mole of an aluminum halide in which the halogen has an atomic number in the range of 17 to 53, then heating the mixture to a temperature of from about 70 C'. to about 130 and maintaining the mixture at the latter temperature until the methylation re action is substantially complete.

25. The process for making tetramethyl lead which comprises initiating at a temperature of from about 50 C. to about 70 C. the reaction of a sodium lead alloy and an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53 in the presence of from about 001m about 0.1 atom of aluminum per atom of sodium in said alloy, said aluminum being in the form of a complex aluminum hydride having the formula MAlH wherein M is an alkali metal, and, for each 2 to 4 moles of said complex aluminum hydride, about 1 mole of an aluminum halide in which the halogen has an atomic number in the the range of 17 to 53, then heating the mixture to a temperature of from about C. to about C. and maintaining the mixture at the latter temperature until the methylation reaction is substantially complete.

26. The process for making tetramethyl lead which comprises initiating at a temperature of from about 50 C. to about 70 C. the reaction of monosodium lead alloy and an alkylating agent which consists of methyl chloride in the presence of from about 0.01 to about 0.1 atom of aluminum per atom of sodium in said alloy, said aluminum being in the form of lithium aluminum hydride, and, for each 2 to 4 moles of said lithium aluminum hydride, about 1 mole of aluminum chloride, then heating the mixture to a temperature of from about 100 C. to about 130 C. and maintaining the mixture at the latter temperature until the methylation reaction is substantially complete.

References Cited in the file of this patent UNITED STATES PATENTS 2,270,108 Calingaert et al. Jan. 13, 1942 2,270,109 Calingaert et al. Jan. 13, 1942 2,695,327 Ziegler et al. Nov. 23, 1954 OTHER REFERENCES J. Inorg. Chem, 1958, vol. 6, pp. 134137 (London). 

1. THE PROCESS FOR MAKING TETRAMETHYL LEAD WHICH COMPRISES MIXING AT A TEMPERATURE BELOW 50* C. A SODIUM LEAD ALLOY, AT LEAST ABOUT 0.25 MOLE PER MOLE OF SODIUM OF AN ALKYLATING AGENT WHICH CONSISTS OF A METHYL HALIDE IN WHICH THE HALOGEN HAS AN ATOMIC NUMBER IN THE RANGE OF 17 TO 53, AND IN AN AMOUNT TO PROVIDE FROM 0.003 TO ABOUT 0.3 ATOM OF ALUMINUM PER ATOM OF SODIUM IN SAID ALLOY, AN ALUMINUM-CONTAINING HYDRIDE OF THE GROUP CONSISTING OF ALUMINUM HYDRIDE, COMPLEX ALUMINUM HYDRIDES HAVING THE FORMULA M(AIH4)N WHEREIN M IS A METAL OF THE GROUP CONSISTING OF ALKALI METALS AND ALKALINE EARTH METALS AND N IS AN INTEGER CORRESPONDING TO THE VALENCE OF M, ALUMINUM BOROHYDRIDE, ALKYL ALUMINUM HYDRIDES HAVING THE FORMULA RXAIH3-X WHEREIN R IS AN ALKYL RADICAL OF 1 TO 10 CARBON ATOMS AND X IS AN INTEGER OF 1 TO 2, AND COMPLEX ALKYL ALUMINUM HYDRIDES HAVING THE FORMULA M(RYAIH4-Y)N WHEREIN M IS A METAL OF THE GROUP CONSISTING OF ALKALI METALS AND ALKALINE EARTH METALS, N IS AN INTEGER CORRESPONDING TO THE VALENCE OF M, R IS AN ALKYL RADICAL OF 1 TO 10 CARBON ATOMS AND Y IS AN INTEGER OF 1 TO 3, HEATING THE MIXTURE TO A TEMPERATURE OF FROM 50* C. TO ABOUT 70* C. TO INITIATE THE METHYLATION REACTION AND THEN HEATING THE MIXTURE TO A TEMPERATURE OF FROM ABOUT 70* C. TO ABOUT 130* C. AND MAINTAINING IT AT SUCH TEMPERATURE UNTIL THE METHYLATING REACTION IS SUBSTANTIALLY COMPLETE WHILE GRADUALLY ADDING SUCH QUANTITIES OF SAID METHYL HALIDE AS MAY BE REQUIRED TO PROVIDE A TOTAL OF AT LEAST ONE MOLE THEREOF FOR EACH MOLE OF SODIUM. 